Hydrodynamics of estuaries vol. 1. Estuarine physics, edited by Bjorn Kjerfve, CRC press Boca Ralcon, Florida, 1988. No of pages: 163
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Abstract. Salt intrusion in estuaries has been exacerbated by climate change and human activities. Previous studies have primarily focused on salt intrusion in the mainstem of estuaries, whereas those in sub-estuaries (those branch off their main estuaries) have received less attention. During an extended La Niña event from 2021 to 2022, a sub-estuary (the East River estuary alongside the Pearl River Estuary, China, experienced severe salt intrusion, posing a threat to the freshwater supply in the surrounding area. Observations revealed that maximum salinities in the main estuary typically preceded spring tides, exhibiting significant asymmetry in salinity rise and fall over a fortnightly timescale. In contrast, in the upstream region of the sub-estuary, the variation of salinity was in phase with that of the tidal range, and salinity rise and fall exhibited more symmetrical. Inspired by these observations, we employed idealized numerical models and analytical solutions to investigate the underlying physics behind these behaviors. It was discovered that under normal dry condition (with a river discharge of 1500 m3 s-1 at the head of the main estuary), the river-tide interaction and change in horizontal dispersion accounted for the in-phase relationship between the salinity and tidal range in the upstream region of the sub-estuary. Under extremely dry conditions (i.e., a river discharge of 500 m3 s-1 at the head of the main estuary), salinity variations kept pace with those of the tidal range from the middle to upstream regions of the sub-estuary. The variation of salinity in the main estuary, along with those of salt dispersion and freshwater influx inside the sub-estuary collectively influenced salinity variation in the well-mixed sub-estuary. These findings have important implications for water resource management and salt intrusion prevention in the catchment area.
Tidal range
Saltwater intrusion
Discharge
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Abstract Estuary is an exclusive system and have an important role but also have vulnerabilities that can threaten life in the estuary region, so it is necessary to have knowledge of estuarine boundaries so that conservation can be maintained. This study aims to analyze the boundaries of the Cimandiri Estuary and the Cisadane Estuary based on surface water salinity, and analyze the relationship of estuarine surface water salinity with rainfall, sea surface currents and tides in the Cimandiri Estuary and Cisadane Estuary. The variables used in this study are salinity, rainfall, sea surface currents, and tides. The research method use the Cimandiri Algorithm by processing OLI Landsat 8 Imagery in 2018 and 2019. The results of this study are estuary boundaries divided into 3 estuary boundary classes specifically Mexo-oligohaline (0.5-5 ‰), Mexo-mesohaline (5-18 ‰), and Mexo-polyhaline (18-30 ‰). Cimandiri’s salinity value is strongly affected by season, then by tides and last by the currents, it is because the Cimandiri Estuary has a deep waters. Meanwhile in the Cisadane Estuary, the salinity value is strongly influenced by season, then by the currents and tides, and also influenced by freshwater from land, it is because the Cisadane Estuary has a shallow water.
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Observations on the planktonic shrimp, Neomysis americana (Smith), in the Delaware River estuary were carried out over a period of two years. It was found that Neomysis was far more abundant in the deep water of the estuary than in the near‐surface or shallow water. Moreover, it was more abundant within the estuary than in the coastal waters at the mouth of Delaware Bay. Measurements of the length of the animal showed increase in size from the ocean toward the river end of the estuary. These features are interpreted in light of the probable circulation of the estuary to show that the animals became older during their “up‐estuary” drift in deep water. Furthermore, they tended to accumulate within the estuary due to their avoidance of the out‐flowing surface waters. A principal source for Neomysis in the coastal waters outside the Bay is thus suggested. During spring and summer, however, reproduction within the Bay contributed to the stock of animals there. The up‐estuary extent of Neomysis was related to the 4‰ isohaline, and the partial exclusion from surface waters was attributed to their avoidance of excessive light.
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Yangtze river
Saltwater intrusion
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